An example of conventional thermal printhead is shown in FIG. 6 (See Patent Document 1 below). The illustrated thermal printhead B includes a substrate 91 and a plurality of heating portions 92 formed on the substrate. The heating portions 92 are aligned in the primary scanning direction and grouped into pairs. As shown in the figure, in each of the pairs, the respective lower ends of the heating portions 92 are connected to each other by an intermediate electrode 93. In each pair, the upper end of the left heating portion 92 is connected to an individual electrode 94, whereas the upper end of the right heating portion 92 is connected to an individual electrode 95. For instance, when power is supplied between the individual electrodes, current flows from the left heating portion 92 to the right heating portion 92 through the intermediate electrode 93. As a result, the paired heating portions 92 are heated to function as a single print dot.
Recently, there is an increasing demand for high-definition thermal printers. To meet this demand, the heating portions need to have a finer structure. To make the conventional heating portions 92 fine, it is necessary to reduce the width of the individual electrodes 94, 95 and the intermediate electrode 93. However, when the width is reduced, the amount of current which can be caused to flow through the electrodes is reduced, so that the current to be supplied to the heating portions 92 becomes insufficient. As a result, the time required for raising the temperature of the heating portions 92 to a temperature suitable for printing increases, so that the printing speed of the thermal printer is reduced.
Patent Document 1: JP-A-2003-165239